Modbus communication fails using MAX485

I have a wierd issue going on with Serial communication . whenever I switch on 9V DC Power supply(9V DC, 1Amp rated) (not connected to Audrino at all ) but near by , the serial communication fails . I suspect that the MX485 TTL Board not able to handle noise. If Power supply is switched off communication gets back to normal. Please note this Power supply is just very near and not connected to Audrino. if I move the PS to more than 2-3 Meters then the circuit works. Anyone faced similar issue ? Any solution? I used Audrino uno with MAX485 Shield for Modbus.


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Curious problem! :astonished:

Are you saying that the problem persists all the while the offending power supply is switched on? If so, something is clearly very wrong.

I think we need a very clearly taken picture with plenty of light, of your arrangement to see what the clue is. :grinning: